Non-impact recording by the ink jet method is becoming popular for converting image data in the form of electrical signals into hard copies because less noise is produced during recording than in the impact recording. The ink jet method is also considered particularly useful because ordinary paper can be used without need for a special process, such as fixing, for recording purposes.
The ink jet method that is already in use comprises the steps of filling an airtight container with ink, applying a pressure pulse thereto, and sending the ink out of an orifice of the container in a jet for recording purposes. The ink jet means in the aforesaid method cannot be made compact in view of its operating mechanism, and the ink jet recorder must be scanned mechanically if recording is to be made with a desired image density. This latter requirement greatly reduces recording speed. At the same time, there have been proposed techniques for remedying shortcomings inherent in the ink jet method and making high-speed recording possible.
The magnetic ink jet method is a typical example of such improvement, which comprises arranging magnetic ink close to a magnetic electrode array, forming an ink-jet state corresponding in position to a picture element by making use of a swell of the ink in the presence of a magnetic field, and jetting the magnetic ink in the static electric field. Since this method admits of electronic scanning, high-speed recording becomes possible, but it is still disadvantageous in that not only the selection of ink but also the coloration characteristic of the ink is limited.
Apart from the aforesaid method, there is also well known the so-called plane ink jet method, which comprises arranging ink in a slitlike inkholder in parallel to an electrode array, and jetting the ink in accordance with an electric field pattern formed between an electrode facing the electrode array through recording paper. Since no minute orifice for storing ink is required in this method, ink clogging can be prevented. However, high voltage applied for jetting the ink makes it necessary to drive the electrode array on a time division basis to prevent a voltage leak across the adjoining or neighboring electrodes and prevent the recording speed from being increased to the extent intended.
There has also been proposed the so-called heat bubble jet method for jetting ink out of an orifice by means of thermal energy. In this method, the ink is abruptly heated to cause film boiling and a pressure rise resulting from the rapid formation of bubbles within the orifice is utilized to jet the ink out thereof. However, the film boiling temperatures are as high as 500.degree.-600.degree. C. and this makes it difficult to put the aforesaid method to practical use because the ink properties tend to change with temperature and because the heating resistor protective layer provided as a heating means is deteriorated at the high temperatures employed in this method.
As set forth above, there are remaining problems to be practically solved in the ink jet methods heretofore developed, the problems including difficulty in sufficiently increasing recording speed, necessity of employing special ink and contriving a particular driving means, and thermal deterioration that the ink and the heating means are expected to undergo.